This invention relates to an improved self-locking nut. More particularly, it relates to a self-locking nut of the type having a cylindrical end compressed by a helical spring.
Some types of self-locking nuts are known which have a cylindrical or the like end provided with vertical slots which define circular arc segments adapted to be resiliently compressed by a radially acting helical external spring.
One of these nuts is described in U.S. Pat. No. 3,417,801 assigned to Bemex, France, which will now be described by way of example.
Although this nut may be considered efficient with regard to resisting vibrations it still has some operative disadvantages which become particularly apparent when the nut is to be re-used after some application. In fact, as the vertical slots at the cylindrical end or collar are very narrow, the dirt and foreign matter which will penetrate into the slots during use cannot be expelled when the collar is contracted by the external spring after unscrewing the nut. For re-using the nut it is therefore necessary to effect a long and expensive cleaning operation by compressed air, solvents or mechanical means, which constitutes the first one of the aforementioned disadvantages.
Further, as the walls of the slots are very close to one another, their range of resilience or compressibility by the spring is very limited because after a certain degree of bending in the radial direction, the upper edges of the circular arc segments contact one another. The structural limitation of the compressibility of the collar impairs the adaptability of the nut to screws or rods having a "lean" thread and thus constitutes a further severe disadvantage.